I use fluorite black sand, make sure to rinse it REALLY well, or you will have a nice cloudy mess in your tank, but its great media for planted tanks, I really like it, and it looks great in my 40 gallon osaka tank.
As for the python, definetly your best bet! You can cut the cost buying the 25' and then making your own extension with bulk 1/2" tubing and a coupling device, or just making your own as well with buying the parts and tubing. There are a few other manufacturers such as Lee's and Marina who also make them.
Seachem has a calculator on how many bags of fluorite you would need for your tank, I usually do about a 2" substrate. (Scroll down to bottom and enter tank dimensions)
Seachem. Flourite Black Sand